Growing demand for air conditioning in recent years has caused a significant increase in demand for electrical energy. Global warming, now an undisputed fact, has led to an increase in air conditioning demand not only in hot and humid climates such as in Mediterranean and equatorial countries, but also in European countries with limited air conditioning tradition. Electric utilities have their peak loads on hot summer days, and are often barely capable of meeting the demand, struggling with brown-out situations. With suitable technology, solar cooling systems can help alleviate, if not eliminate the problem. This is a good application for solar energy as the greatest demand for air conditioning occurs during times of peak solar radiation.
A liquid desiccant air-conditioning/dehumidification system is a good alternative to an electric-powered conventional cooling system. Liquid desiccant air-conditioning systems operate essentially as open-cycle absorption devices. Such systems are capable of using industrial waste heat or low-grade solar heat from low-cost flat plate collectors as their source of power, and have the potential to provide both cooling and dehumidification, as required by the load.
Liquid desiccant systems in their “pure” configuration typically provide dehumidified air and not necessarily cooled air. However, a heat exchanger for cooling the dry air can be added, which may even include the addition of a small amount of water to the dried air in order to lower its temperature, while still keeping the air at a comfortable humidity level. Moreover, in many situations and climates, the dehumidification aspect of air conditioning is the most important component of the air conditioning process; and downstream cooling may not be necessary.
Liquid desiccant systems typically include a dehumidifying (absorber) section for removing moisture from humid fresh (or re-circulated) air, by a hygroscopic solution; and a regeneration (desorber) section for re-concentrating the hygroscopic solution, i.e. removing from it a portion of the absorbed moisture.
Examples of such systems are disclosed in U.S. Pat. No. 2,672,024 (McGrath); U.S. Pat. No. 2,798,570 (Kelley); U.S. Pat. No. 6,487,872 (Forkosh et al.); and U.S. Pat. No. 6,546,746 (Forkosh et al.).